This invention relates to coating composition systems suitable for use as weatherstrip coatings. In particular, it relates to silicone compositions that are water reducible and, when applied to common weatherstrip material such as EPDM rubber, provide a coating that possesses properties such as low coefficient of friction, improved abrasion resistance and freeze-release.
A wide variety of OH-terminated diorganosiloxane coatings having freeze-release properties are known and are readily available. Most of the coatings are used to treat paper and other porous substrates such that the adhesion of-the coating to the substrate is primarily based on physical anchorage. On non-porous substrates such as plastics and rubber surfaces, adhesion of these coatings is poor. Furthermore, these coatings have little resistance to removal by abrasion. Because of these problems coating systems for non-porous substrates often require two process steps including the application of a primer followed by the application of the coating material as is taught in for example U.S. Pat. No. 4,233,428 of Endo.
One step coating compositions have been taught by Sumida in U.S. Pat. No. 4,252,933 issued Feb. 24, 1981. Further, an amine functional silane modified epoxy resin composition has been taught in my Canadian Patent Application S.N. 2,034,851 filed Jan. 24, 1991 and due to be laid open for public inspection on Jul. 25, 1992.
Although the above mentioned coating composition for non-porous substrate provides an abrasion resistant film having good freeze-release properties, it contains large amounts of organic solvents. Typical coating bath contains over 90% solvents such as chlorothene and toluene. Industry is moving away from coatings containing high levels of organic solvent and the development of a water based or water reducible coating for use as weatherstrip coating is highly desirable.
Water based silicone coatings such as paper releases and polishes are known and available. For example, a water based polish is taught by Traver et al in U.S. Pat. No. 4,600,436 issued Jul. 15, 1986 and assigned to General Electric Company. The polish, an amine functional silicone emulsion, is a reaction product of a diorganopolysiloxane fluid, an aminofunctional silane, a polymerization catalyst and water.
There is no teaching of a one step application for a water reducible silicone system for use as weatherstrip coating. It has been discovered that this water reducible weatherstrip coating has low coefficient of friction, good abrasion resistance and freeze release properties while avoiding the problems associated with the use of large amounts of solvent.